Gary Neville believes Sir Alex Ferguson's retirement will serve as added motivation for Manchester United as they look to defend their Premier League title next season.

Ferguson's departure from Old Trafford sparked a number of changes to the back-room staff, with some critics claiming David Moyes should not be expected to win the league during his first season in charge.

United's rivals may feel their own fortunes have been boosted, but Neville insists the adjustments will be an aid rather than a hindrance for his former club.

"They should see it as a new challenge and an important challenge," Neville told Manchester United's official website. "Since Sir Alex announced his retirement other clubs have already been lifted by the fact he is no longer around.

"The players should see that as a slight on them and say 'Hang on, do you think we can't go out on that pitch and perform without our manager?'

"That is a challenge in itself and ultimately the players and David Moyes will need to respond to that. It won't be a bed of roses - there will be ups and downs as there always are and there have been over the last 26 or so years.

"There will be pressure moments in the coming season when people will say 'it's not the same' but it's too easy to say that."

Neville has described United's current title-winning side as one of the four greatest teams Ferguson led during his 26-year reign, insisting Moyes already has a successful squad at his disposal.

"He is a manager who has built four great teams - 94, 99, 2008 and you can now argue this one that has won the league - people are always going to compare teams," Neville added.

"The most important thing to say about this team is it's on an upward curve. You've got players like (David) De Gea, Rafael, (Jonny) Evans, (Chris) Smalling, (Phil) Jones, (Tom) Cleverley, (Danny) Welbeck and (Javier) Hernandez to name eight players who are still young and haven't reached anywhere near their peak.

"You've also got a mix of players in the middle who are at their peak then you've got the experienced lads at the other end. This team has still not reached its potential. I'm sure there will be additions to the squad this summer so you're talking about a team on the up."